Switching circuit



y 1957 J. o. EKBLOM ETAL 2,791,724

SWITCHING CIRCUIT Filed July 31, 1953 2 Sheets-Sheet 1 INVENTORS JOHN O. EKBLOM Lzdmno E. RAVICH ATTORNEYS y 1957 J. o. EKBLOM ETAL 2,791,724

SWITCHING CIRCUIT Filed July 31, 1953 2 Sheets-Sheet 2 QAl ll wi l INVENTORS 9 4 JOHN C. EKBLOM LEONARD E. RAVICH ATTORNEYS SWITCHING CIRCUIT John 0. Ekblom and Leonard E. Ravich, New York,

N. Y., assignors, by mesne assignments, to Hnpp Corporation, Cleveland, Ohio, a corporation of Virginia Application July 31, 1953, Serial No. 371,668

17 tilaims. (Cl. 315-153) The present invention relates to ignition systems for internal combustion engines, and more particularly to improvements so that the production-and distribution of pulses of electrical energy are accomplished without the use of moving contacts.

In the prior art ignition systems for internal combustion engines it has become the general practice to provide a low voltage, high current, primary circuit interrupted by a cam operated switch, and inductively coupled to a high voltage, low current secondary circuit provided With a rotating contact arm sequentially establishing electrical contact with the spark plug circuits of the several cylintiers of the engine.

In such systems of the prior art there is troublesome deterioration of the contact points of the switch in the primary circuit, and improper operation of the ignition system is caused by faulty operation of the high tension distributor due to the burning of contacts and due to the presence of dirt and moisture.

To overcome these disadvantages of the prior art ignition systems, it is a fundamental object of the present invention to provide an ignition system in which pulses of electrical energy are produced and distributed to the several spark plugs Without the use of moving contacts.

It is a further important object of this invention to provide an ignition system in which the initiation and termination of primary current flow is controlled by a radiation sensitive element intermittently rendered conductive by radiant energy.

It is a further important object of the present invention to provide an improved ignition system having a high tension current distributing device effective to sequentially connect a series of spark plugs, or like spark gap devices, into the high tension circuit without the use of moving contacts. More specifically it is an object of this invention to provide an improved ignition system in which the distribution of the high tension current is effected by the sequential stimulation of a series of radiant energy responsive elements from an associated source of radiant energy, and with each radiant energy responsive element connected to an individual spark gap device.

It is a further important object of this invention to provide an improved ignition system in which novel means are provided for the production of pulses of electrical energy.

These and other objects of the present invention will become more fully apparent by reference to the appended claims and as the detailed description of the invention proceeds with reference to the accompanying drawings, wherein:

Figure l is a diagrammatic showing of the electrical circuits and components of the ignition system of the present invention;

Figure 2, is a diagrammatic showing of the high tension distributor means of the present invention and associated pulse producing means; and

States atent 2,791,724 Patented May 7, 1957 2 Figures 3 and 4 are diagrammatic showings of modified pulse producing means of the present invention.

Referring to Figure 2, a conventional device, indicated generally at 10, produces regularly recurring electrical pulses which are fed to a primary winding 12, of a suit-. able step-up transformer 14, so that pulses of high voltage appear at the terminals of a secondary winding 16, of the transformer. A plurality of spark plugs 18, are connected to the transformer 14, through a novel high tension distributor means, indicated generally at 19, and are installed on the cylinders of an internal combustion engine (not shown) to effect ignition of the gaseous mixture in' the cylinders in the conventional manner. The novel high tension distributor means comprises a group of photoconductive cells 20, arranged in a circle, and each cell is connected by a wire 22, to a spark plug individual to the cell, and

each cell is also connected to a common wire or bus 24,

before a cell by a common driving means 38, on the engine to which the ignition system is applied. The slot 32, is shaped so that each cell is illuminated suddenly and darkened suddenly so that each cell becomes conducting and non-conducting, respectively, to bring about a result analogous to the closing and opening of a switch but without sparking contacts in the distributor. The cells are formed of one of the binary compounds and of which cadmium sulfide is'preferred, and it is;

characteristic of the cadmium sulfide cell that its internal resistance drops suddenly to an adequately low value when the cell is suddenly illuminated by a light of high intensity, and that its internal resistance returns to an adequately high value when the illumination isremoved so that for many practical purposes the cell may be' thought of as a non-conductor when dark. Thestructure and method of formation of such cells is disclosed in copending application Serial No. 329,973 filed January 7,

1953, by Leonard E. Ravic'h, for Semi Conductor'Improvements and Devices for Use of Same." The term dark is used in the sense in which it isused by' those familiar with the application of photosensitive or other radiation sensitive means, and does not mean the complete absence of light or other radiant energy. The cells 20, are each provided with adequate conducting surface so that they are of adequate current carrying capacity without undue I for carrying the current to the spark' plugs energy loss.

If the spark plugs are of the now conventional shielded type there is nothing in the high tension distributor 19, to cause radio interference, and with the absence of moving switch arms, the possibilityof the distributor producing radio disturbances is avoided. This is of first importance to the armed services for the distributor will not disclose the presence of a vehicle orsliip onwhich it is applied.

Referring now to Figure 1, which shows an ignition system provided with novel means for producing recurring electrical pulses of high voltage. A'first gas "discharge tube 42, at a certain assumed instant, is in the non-conducting condition because of the normal bias on its control grid 44, produced by a bias resistor 46, in its grid-cathode circuit, and connected to the grid through a control resistor 48, and getting current through a wire 71, from a battery 60, through a circuit which includes the bias resistor and a resistor '62, which, in one circuit arrangement, is of the order of twenty thousand ohms. At the assumed initial instant, the anode cathode circuit is atfull voltage'becausea capacitor 50, in this circuit is fully 'chargedt'o substantially the voltage of the battery 60. A second gas discharge tube 52,is also non-conducting because its control gzid64, is biased by thevoltage across a resistor 54, shunted by a capacitor 66, as the capacitor 5.0,bleeds slowly through a voltage divider network of resistors'54 and 56 connected to the terminals of the capacitor 50. Since the capacitor 50','is assumed to be fully charged at the instant'considered, about one-fourth of its voltage will appear across the resistor 54, and the capacitor 66.

"The resistor 62, may be considered a component of a voltage divider circuit which includes the resistor 46, and the'connecting Wire 71 is the negative connection for the cathode 73'of'tube 42, and for the negative pole 75, of the capacitor 50. The time-constant of'the circuit which includes the capacitor 50, and the voltage divider network is large compared to the period during which the capacitor remaiiis charged in the normal operation of the pulse producingmeans, so the capacitor may be fairly said to be fully charged at the assumed initial instant.

If,"now, a sharp pulse of the proper voltage and of the proper polarity is applied in the grid-cathode circuit of thefirst tube 42, this tube will instantaneously become conductingl The capacitor 50, is connected in the platecathode circuit of the tube 42, in series withthe primary winding 12, of the transformer 14,'and with the heavy rush of current through the tube when it becomes conducting a pulse of high voltage appears at the terminals of the secondarywinding 16, of the transformer. The capacitor 50 is substantially isolated at the instant of discharge from the positive pole of the battery 60 by the resistor 62. When the capacitorSO, is substantially discharged the plate voltage of the tube 42, drops to a low value so that the control grid 44, regains a control, and the tube becomes again non-conducting.

As the capacitor 50becornes substantially discharged, the small capacitorf66, across the terminals of the resistor 54; discharges slowly through this resistor, and'the second tube 52, becomes conducting to connect the capacitor 50, to the positive pole of the battery 60, to charge the capacitor. "The pathof the charging current is through the tube 52, through the capacitor 50, and through the bias resistor 46, to the negative pole of the battery. This path is 'of relatively low resistance, and the'instantaneous currentwould be large,but for the fact that this instantaneous current is limited by an inductance 68, connected in series inthe plate circuit, and having a low resistance so that the energy loss is low. It has been observed that one effect of this inductance is to materially sharpen the charging current pulse of the capacitor 50, as distinguished from the shape of the pulse if a resistor was inserted in lieu of the inductance as current limiting means. As the capacitor 50,charges through the bias resistor 46, it charges the capacitor 70, connected in shunt with the resistor '46, and there is a temporary high bias voltage established in the control grid circuit of the tube 42. This temporary high bias voltage is useful in preventing un wanted firing of tube 42, while the second tube 52, is conducting, and so avoids possible accidental destruction of'the two tubes. The capacitor 70, discharges through the resistor 46, and the bias of the control grid of the first tube 42, returns to normal when the capacitor 50, attains practically full charge. becomes practically fully charged the plate current of thefsecond tube 52 becomes so low that the'bias voltage now appearing across the resistor 54, enables the control grid 64, to take control and to render the tube 52, nonconducting, so that the system is now ready'to accept a pulse at'the control grid of the first tube 42..

A battery 72, is arranged to'charge a capacitor 74 When the capacitor 50,

through a circuit which includes the battery, an inductance 76, the capacitor, and the grid control resistor. A cadmium sulfide photoconductive cell 78, is connected in parallel with the charging circuit by wires 80, and when this cell is dark its internal resistance is so high that it does not interfere with the charging of the capacitor. A light or other suitable radiant energy source 32 such as tritiated stilbene is disposed in front of the cell, and a revolvable obscuring disc or shutter 34, is disposed be tween the light source and the cell. The shutter is revolvcd in synchronism with the casing 30 of the high tension distributor 19, described in connection with Figure 2, so that slots 36, in the, shutter 84, expose the cell 78, to a burst of light at the instant that a cell 20, is being made conductive in the high tension distributor 19. When the cell 78, becomes illuminated its resistance drops to a relatively very low value so that the capacitor 74, now quickly discharges through a discharging circuit which includes the cell 78, the capacitor, and the resistor 48, and since the resistor 48 is in the grid-cathode circuit of tube 42, the voltage developed across it by the discharge current causes the tube 42 to become conducting. When the tube 42, becomessuddenly conducting a pulse of high voltage appears at the terminals of the secondary winding of' the tra nsformer 14, in the manner already described.

The dotted line 83 is used to indicate that the shutter 84, is connected with the casing 30, of the high tension distributor by suitabiemeans to get the desired synchronizing of the light flashes.

The illuminating of the cell 78, is comparable to the break in the primary circuit of the conventional ignition system in that it results in the pulse of current from the capacitor74, to make the tube 42, conducting to get the spark, and the darkening of the tube is comparable to the make in the primary circuit of the conventional ignition system in that it perm-its energy being stored in the capacitor. However, in the present ignition system there are no moving parts in the electrical circuit, andno moving current-carrying switch parts to be affected by burning, dirt and moisture.

In the pulse producing means shown in Figure 3, a capacitor 87, is charged by a battery 85 in a circuit which comprises the battery, the capacitor, a resistor 88, and a grid'controlling resistor W), in the grid-cathode circuit of a gas discharge tube 92, and with a control grid 94, of the tube connected at the junction of the capacitor to the controlling resistor. A photoconductive cell 96, of cadmium sulfide or another suitable binary compound, has a high resistance when dark, and a relatively very lowresistance when illuminated, and when illuminated it eifects the discharging of the capacitor through a discharging circuit which comprises the capacitor, the cell, and the controlling resistor 90. A light source 93, is disposed in front of the cell, and a revolvable wheel or shutter 109, is interposed between the light source and the cell and is provided with slots 104, shaped to effect a sharp pulse of illumination and a sharp cut-off.

A suitable source 166, of alternating current, feeds the plate-cathode circuit of the tube through a suitabletransformer-J08, and the primary winding 103 of a step-up transformer 102, is inserted in the plate-cathode circuit, and the secondary winding of the transformer may be connected to the revolving contact arm 110, of a conventional high tension distributor 112, to the spark plugs 114, of the internal combustion engine to which the system is applied. As indicated by the dotted line 116, .the revolving wheel or shutter 100, is synchronized with'the revolving arm 11b. The tube is suitably biased by a battery 118, in the grid-cathode circuit of the tube to be non-conducting while the capacitor 87 is charging,

and when the cell 96 becomes suddenly illuminated, the

discharging current of the capacitor through the control resistor 90, producss a bias of the right value to cause the tube to become suddenly conductingif the plate of the tube is positive' The fr equency of the alter nating current source should be at least twice the frequency at which the firing impulses are received at the control grid 94, and the time constant of the capacitor discharging circuit should have a minimum value equal to one complete cycle of the alternating current supplied by the source 106.

The control grid 94, usually gains control of thefiring of the tube when the plate becomes negative, but if the time constant of the grid circuit is high enough current may flow through the tube over more than one positive half cycle, and more than one spark may appear at the spark plug at the top of each piston ignition stroke. However, these sparks are very close together in time, and a short train of sparks following a single activating pulse at the control grid of the tube is not objectionable, since the sparks would occur while the contact arm of the conventional distributor was still in connection with a single spark plug.

In the pluse producing means shown in Figure 4, a capacitor 120, is charged by a battery 122, in a charging circuit which comprises the capacitor, the battery, a resistor 124, and a grid controlling resistor 126, of a beam power tetrode tube 128. A control grid 125, of the tube is connected to the junction of the capacitor and the control resistor 128.

A photoconductive cell 130, is disposed in front of a light source 132, and a revolving wheel or shutter 134, similar to those already described, is provided to alternately illuminate and darken the cell. The cell is of cadmium sulfide, or of another suitable binary compound, and has a high ohmic resistance when dark, and a very low resistance when adequately illuminated. When the cell is illuminated suddenly its resistance drops suddenly and it causes the discharging of the capacitor 120, through a discharging circuit which comprises the capacitor, the cell, and the grid controlling resistor 126, and the voltage developed across the resistor 126, causes the tube 128 to become conducting. The tube is normally biased to near cut-off condition by a battery 136, connected to a voltage divider having a portion 138, in the grid-cathode circuit of the tube, and a portion in the circuit connecting a screen grid of the tube with the cathode of the tube, and shunted by a capacitor 144.

A primary winding 146, of a pulse transformer 148, is connected in the plate circuit of the tetrode 128, and a secondary winding 150, of the pulse transformer is inserted in the plate circuit of ,the gas discharge tube 152, in series with a primary winding 151, of a step-up transformer or spark coil 153. The secondary winding 150, is so connected in the plate circuit of the tube 152, that when the tetrode 12S, becomes suddenly conducting there is a pulse of voltage injected in the plate circuit of the tube 152, opposing the plate voltage to assist in momentarily changing the tube 152, from the conducting to the non-conducting condition.

At the instant at which the plate voltage of the tube 152, drops because of the opposing voltage from the pulse transformer, a control grid 154, gains control of the tube to render it non-conducting because of the bias voltage available through a bias resistor 156 in the gridcathode circuit, and shunted by a capacitor 158. The sudden interruption of the plate current of the tube 152, results in a sudden collapse of the magnetic field of the spark-coil 153, and a pulse of high voltage appears at the terminals of a secondary winding 160, of the spark coil.

With the termination of the pulse from the pulse transformer 148, and the subsequent increase in the plate volttage of the tube 152, the control grid 154, loses control, and the tube 152, begins to conduct again with the increase in its plate current somewhat delayed by the inductance of the primary winding of the spark coil 153.

The output of the transformer 153, is fed to the spark plugs of the internal combustion engine through a suitable high tension distributor, indicated generally at 162, and, as in the ignition systems hereinbefore described the movement of shutter 134, is synchronized with the distributing means in the distributor 162, as indicated by the dotted lines 164.

While the pulse producing means hereinbefore de-' scribed are peculiarly adapted to meet the requirements of the ignition system of an internal combustion engine, it will be understood that the pulse producing means are not limited in their application to such systems, and have utility apart from such systems, and that other uses and applications of the inventions disclosed and modifications thereof will be obvious to those skilled in the art without departing from the spirit and the scope thereof.

The invention may be embodied in other specific forms without departing from the spirit of essential character-' istics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not re-' strictive, the scope of the invention being indicated by the appended claims rather than by the foregoing de-" scription, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In an internal combustion engine ignition system having a primary circuit, a high voltage secondary circuit inductively coupled to said primary circuit, and a plurality of spark plugs adapted to be energized by said secondary circuit, means for selectively energizing said spark plugs with voltage from said secondary circuit comprising a plurality of radiation sensitive elements in-' dividual to each of said spark plugs connected to said secondary circuit, a source of radiant energy, and means operative to efiect sequential radiation of said elements from said source to sequentially render said elements conductive.

2. In an ignition system for an internal combustion engine, means for producing electricalpulses, a spark gap, a photoconductive cel-l connected in series circuit association with said pulse producing means source and with said spark gap, a source of radiant energy, and means controlling radiant energy from said source to said cell to render said cell alternately conducting and non-conducting, respectively.

3. In an ignition system for an internal combustion engine, means for producing high voltage electrical pulses, a spark plug, a photoconductive cell in series circuit relation between said spark plug and said source, and means to selectively illuminate said cell to conductively connect said spark plug with said source only during the period of a selected pulse. I

4. An ignition system for an internal combustion engine, comprising means for producing pulses of high voltage, a plurality of spark plugs, a photoconductive cell inserted in series circuit relation between each spark plug and said source, and means to sequentially and intermit-.

tently illuminate said cells to conductively connect a selected spark pluk for the passing of 'a selected pulse thereto at a given instant, and to impede the passing of the selected pulse to the other spark plugs at that instant.

5. An electrical system comprising a source of electrical pulses, a load circuit, a photosensitive cell having a high resistance when dark and a low resistance when illuminated connected in series circuit relation between said load circuit to said source and normally prevent said pulse from being transmitted to said load circuit in nonconductive relation to said source, and means to selectively illuminate said cell to efiect the conductive connection of said load circuit to said source for the passage of a selected pulse to said load circuit from said source.

6. In an ignition system for internal combustion engines, a first photoconductive cell, a first means to intermittently illuminate said first cell, a second photoconductive cell, a second means to intermittently illuminate said second cell in synchronism with the illuminating of '7' said -first cell, means to produce pulses of high voltage connected inci-rcuit association with said first cell and with said second cell and controllable by said first cell, and a spark plug connected to be energized by said pulse producingrneans through said second cell.

7. 'In an ignition system for internal combustion engines, a photoconductive cell, a source of direct current, aneleotron tube having a grid circuit, a capacitor in a control grid circuit of said electron tube, said capacitor being connected to said direct current source to be charged thereby and to said cell to be discharged when said cell is illuminated, means tocyclica-lly illuminate and darken said cell, to thereby control discharge and charge of said capacitor, respectively, a spark gap in circuit association with said electron tube, and means responsive to current conduction in said tube to produce pulses of voltage at said-gap.

8. :In the ignition means of claim 7, said electron tube means comprising a gas discharge tube having a control grid, a cathode. and an anode, a bias voltage battery connected tosa-id control gridand to said cathode, a source of alternating current connected to said cathode and to said anode, a resistor connected to said control grid and to said cathode, and connected in the path of the charging and discharging current of said capacitor, respectively.

9. in an ignition system for an internal combustion engine, means for producing electrical pulses, a spark gap, 21 cadmium sulfide photoconductive cell connected in series circuit association with said means and with said spark gap through which said pulses are conducted, a source of radiant energy, and means controlling energy radiatingfrom said source to said cell to render said cell alternately conducting and non-conducting respectively.

10. -In an ignition system for an internal combustion engine, means for producing electrical pulses, a spark gap, a photoconductive cell formed of a binary compound connected in series circuit association between said means and said spark gap through which said pulses are conductive, a source of radiant energy, and means controlling radiant energy from said source to said cell to render said cell alternately conducting and non-conducting, respectively.

1l. An ignition system for internal combustion engines, comprising a first photoconductive cell, a first means to alternately illuminate and darken said cell, respectively, a group of photoconductive cells including a second photoconductive cell, spark plugs connected to said cells, means to produce pulses of high voltage connected in circuit associationswi-th said first cell and with said group of cells, and controllable by said first cell, and means to alternately illuminate and darken said second cell, rcspectivcly, in synchronism with selected illumination of said-firsticell.

12. In an ignition system for an internal combustion engine, a beam power tetrode tube including a control grid, means normally biasing said control grid to render saidtube substantially non-conducting, a spark coil having a primary winding and having a secondary winding, a sparlcplug connected to said secondary Winding, a gas 8 discharge .tube connected normally maintaining current flow through said primary winding, pulse producing means operatively connected to said control grid to apply a pulse of voltage to said control grid to render said tetrodeconducting, and means in circuit association with said tetrode tube and inductively coupled to means in circuit association with said gas discharge tube to render said gas discharge tube non-conducting when said tetrode tube becomes conducting and thereby interrupt current flow in said primary winding.

13. In an ignition system for an internal combustion engine, a first gas discharge tube having a control grid, a cathode and an anode, an initially charged capacitor, a transformer having a primary winding, said capacitor and said primary winding being connected in series and in a circuit connecting said anode with said cathode, a second gas discharge tube having a control grid, a cathode and an anode, means connecting said control grid and said cathode of said second tube to said charged capacitor to render said second tube non-conducting, pulse producing means connectedto said control grid of said first tube to apply a pulse of voltage thereto and render said first tube conducting to thereby discharge said capacitor through said primary winding, a secondary Winding on said transformer, a spark plug connected to said secondary winding, means operative upon the discharging of said capacitor to render said first tube non'conducting, a battery, and means operative upon the discharge of said capacitor to render said second tube conducting to thereby conductively connect said capacitor with said battery to restore the charge to said capacitor.

14. The ignition means of claim 13, with the addition of means in circuit association with said capacitor and with said control grid of said first tube and operative during the restoration of charge to said capacitor to provide a high negative bias to said control grid.

15. In the ignition means of claim 13, the provision of an inductance in series with said battery and operative to limit the initial flow of current to said capacitor when it is connected to said battery to restore its charge.

16. In the ignition means of claim 13, with said pulse producing means comprising a capacitor, a battery, and a photosensitive cell in circuit association and means to alternately render said cell conducting and non-conducting, respectively.

17. In an electrical circuit, a first electrical conductive channel, a plurality of electrically conductive channels distinct from said first channel, a like plurality of compound type radiation sensitive elements each connected to one of said plurality of channels and to said first channel, a source of radiant energy and means operative to eiiect stimulation of selected ones of said elements.

References Cited in the file of this patent UNITED STATES PATENTS 

